サブネット計算
ネットワークと新しいプレフィックス長を選んで、同じ大きさのサブネットに分割します。
/24 のサブネット 4 個
| # | ネットワークアドレス | 利用可能な範囲 | ブロードキャストアドレス | 利用可能なホスト数 |
|---|---|---|---|---|
| 1 | 10.0.0.0/24 | 10.0.0.1 – 10.0.0.254 | 10.0.0.255 | 254 |
| 2 | 10.0.1.0/24 | 10.0.1.1 – 10.0.1.254 | 10.0.1.255 | 254 |
| 3 | 10.0.2.0/24 | 10.0.2.1 – 10.0.2.254 | 10.0.2.255 | 254 |
| 4 | 10.0.3.0/24 | 10.0.3.1 – 10.0.3.254 | 10.0.3.255 | 254 |
このテキストはまだ日本語で提供されていません。翻訳が公開されるまで英語で表示しています。
Subnetting divides one network into smaller, equally sized networks by lengthening the prefix. Every extra bit doubles the number of subnets and halves their size: a /24 split into /26 gives four networks of 64 addresses each.
Pick a network and the new prefix length. The table lists each resulting subnet with its usable range — useful for planning VLANs, cloud VPC subnets or IPv6 site allocations. For IPv6, the common unit for a single LAN is a /64; sites typically receive a /48 or /56.
よくある質問
How do I split a /24 into four subnets?
Use /26. Adding two bits to the prefix (24 + 2) creates 2² = 4 subnets of 64 addresses: .0/26, .64/26, .128/26 and .192/26.
Why should IPv6 LANs use /64?
SLAAC address autoconfiguration and many IPv6 features assume a 64-bit interface identifier, so subnets smaller than /64 break standard behaviour.
Can subnets be different sizes?
Yes — that is variable-length subnet masking (VLSM). Calculate each block separately and make sure the ranges don't overlap.